: A First-Principles Thermochemical Descriptor for Predicting Molecular Synthesizability.

Predicting the synthesizability of a new molecule remains an unsolved challenge that chemists have long tackled with heuristic approaches. Here, we report a new method for predicting synthesizability using a simple yet accurate thermochemical descriptor. We introduce , the energy difference between a molecule and its lowest energy constitutional isomer, as a synthesizability predictor that is accurate, physically meaningful, and first-principles based.

2D Ionic Liquid-Like State of Charged Rare-Earth Clusters on a Metal Surface.

Rare-earth complexes are vital for separation chemistry and useful in many advanced applications including emission and energy upconversion. Here, 2D rare-earth clusters having net charges are formed on a metal surface, enabling investigations of their structural and electronic properties on a one-cluster-at-a-time basis using scanning tunneling microscopy. While these ionic complexes are highly mobile on the surface at ≈100 K, their mobility is greatly reduced at 5 K and reveals stable and self-limiting clusters.

A solid-state Li-air battery: computational studies of interfaces and relevance to discharge mechanism.

There is much interest in developing new energy storage systems to replace currently available ones that mainly work based on Li-ion intercalations. One attractive area is the Li-air battery for which most of the research has involved liquid electrolytes. There have been few studies on the use of a solid electrolyte in a Li-air battery.

Template assisted lithium superoxide growth for lithium-oxygen batteries.

Developing batteries with energy densities comparable to internal combustion technology is essential for a worldwide transition to electrified transportation. Li-O batteries are seen as the 'holy grail' of battery technologies since they have the highest theoretical energy density of all battery technologies. Current lithium-oxygen (Li-O) batteries suffer from large charge overpotentials related to the electronic resistivity of the insulating lithium peroxide (LiO) discharge product.

Light- and Chemical-Doping-Induced Magnetic Behavior of Eu Molecular Systems.

Variable temperature electron paramagnetic resonance (VT-EPR) was used to investigate the role of the environment and oxidation states of several coordinated Eu compounds. We find that while Eu(III) chelating complexes are diamagnetic, simple chemical reduction results in the formation of paramagnetic species. In agreement with the distorted symmetry of Eu molecular complexes investigated in this study, the EPR spectrum of reduced complexes showed axially symmetric signals ( = 2.

Triarylmethyl cation redox mediators enhance Li-O battery discharge capacities.

A major impediment to Li-O battery commercialization is the low discharge capacities resulting from electronically insulating LiO film growth on carbon electrodes. Redox mediation offers an effective strategy to drive oxygen chemistry into solution, avoiding surface-mediated LiO film growth and extending discharge lifetimes. As such, the exploration of diverse redox mediator classes can aid the development of molecular design criteria.

Accurate Prediction of Adiabatic Ionization Potentials of Organic Molecules using Quantum Chemistry Assisted Machine Learning.

In previous work (Dandu et al., . .

A room temperature rechargeable LiO-based lithium-air battery enabled by a solid electrolyte.

A lithium-air battery based on lithium oxide (LiO) formation can theoretically deliver an energy density that is comparable to that of gasoline. Lithium oxide formation involves a four-electron reaction that is more difficult to achieve than the one- and two-electron reaction processes that result in lithium superoxide (LiO) and lithium peroxide (LiO), respectively. By using a composite polymer electrolyte based on LiGePS nanoparticles embedded in a modified polyethylene oxide polymer matrix, we found that LiO is the main product in a room temperature solid-state lithium-air battery.

An SECM-Based Spot Analysis for Redoxmer-Electrode Kinetics: Identifying Redox Asymmetries on Model Graphitic Carbon Interfaces.

The fundamental process in non-aqueous redox flow battery (NRFB) operation revolves around electron transfer (ET) between a current collector electrode and redox-active organic molecules (redoxmers) in solution. Here, we present an approach utilizing scanning electrochemical microscopy (SECM) to evaluate interfacial ET kinetics between redoxmers and various electrode materials of interest at desired locations. This spot-analysis method relies on the measurement of heterogeneous electron transfer rate constants (k or k ) as a function of applied potential (E-E ').

A KMnO-Generated Colloidal Electrolyte for Redox Mediation and Anode Protection in a Li-Air Battery.

The rechargeable lithium-oxygen (Li-O) battery has the highest theoretical specific energy density of any rechargeable batteries and could transform energy storage systems if a practical device could be attained. However, among numerous challenges, which are all interconnected, are polarization due to sluggish kinetics, low cycle life, small capacity, and slow rates. In this study, we report on use of KMnO to generate a colloidal electrolyte made up of MnO nanoparticles.

Atomically precise control of rotational dynamics in charged rare-earth complexes on a metal surface.

Complexes containing rare-earth ions attract great attention for their technological applications ranging from spintronic devices to quantum information science. While charged rare-earth coordination complexes are ubiquitous in solution, they are challenging to form on materials surfaces that would allow investigations for potential solid-state applications. Here we report formation and atomically precise manipulation of rare-earth complexes on a gold surface.

Tunable Solid Acid Catalyst Thin Films Prepared by Atomic Layer Deposition.

Solid acid catalysts, including zeolites and amorphous silica-aluminas (ASAs), are industrially important materials widely used in the fuel and petrochemical industries. The versatility of zeolites is due to the Brønsted acidity of the bridging hydroxyl and shape selectivity that can be tailored during and after synthesis. This is in contrast to amorphous silica-alumina, where tailoring acidity is a major challenge as the Brønsted acid structure in ASA is still debated.

Toward Bottom-Up Understanding of Transport in Concentrated Battery Electrolytes.

Bottom-up understanding of transport describes how molecular changes alter species concentrations and electrolyte voltage drops in operating batteries. Such an understanding is essential to predictively design electrolytes for desired transport behavior. We herein advocate building a structure-property-performance relationship as a systematic approach to accurate bottom-up understanding.

Improving the Accuracy of Composite Methods: A G4MP2 Method with G4-like Accuracy and Implications for Machine Learning.

G4MP2 theory has proven to be a reliable and accurate quantum chemical composite method for the calculation of molecular energies using an approximation based on second-order perturbation theory to lower computational costs compared to G4 theory. However, it has been found to have significantly increased errors when applied to larger organic molecules with 10 or more nonhydrogen atoms. We report here on an investigation of the cause of the failure of G4MP2 theory for such larger molecules.

Concentration-dependent ion correlations impact the electrochemical behavior of calcium battery electrolytes.

Ion interactions strongly determine the solvation environments of multivalent electrolytes even at concentrations below that required for practical battery-based energy storage. This statement is particularly true of electrolytes utilizing ethereal solvents due to their low dielectric constants. These solvents are among the most commonly used for multivalent batteries based on reactive metals (Mg, Ca) due to their reductive stability.

Insights into Spontaneous Solid Electrolyte Interphase Formation at Magnesium Metal Anode Surface from Molecular Dynamics Simulations.

Spontaneous chemical reactivity at multivalent (Mg, Ca, Zn, Al) electrode surfaces is critical to solid electrolyte interphase (SEI) formation, and hence, directly affects the longevity of batteries. Here, we report an investigation of the reactivity of 0.5 M Mg(TFSI) in 1,2-dimethoxyethane (DME) solvent at a Mg(0001) surface using molecular dynamics (AIMD) simulations and detailed Bader charge analysis.

One-Dimensional Lateral Force Anisotropy at the Atomic Scale in Sliding Single Molecules on a Surface.

Using a q+ atomic force microscopy at low temperature, a sexiphenyl molecule is slid across an atomically flat Ag(111) surface along the direction parallel to its molecular axis and sideways to the axis. Despite identical contact area and underlying surface geometry, the lateral force required to move the molecule in the direction parallel to its molecular axis is found to be about half of that required to move it sideways. The origin of the lateral force anisotropy observed here is traced to the one-dimensional shape of the molecule, which is further confirmed by molecular dynamics simulations.

Graph-Based Approaches for Predicting Solvation Energy in Multiple Solvents: Open Datasets and Machine Learning Models.

The solvation properties of molecules, often estimated using quantum chemical simulations, are important in the synthesis of energy storage materials, drugs, and industrial chemicals. Here, we develop machine learning models of solvation energies to replace expensive quantum chemistry calculations with inexpensive-to-compute message-passing neural network models that require only the molecular graph as inputs. Our models are trained on a new database of solvation energies for 130,258 molecules taken from the QM9 dataset computed in five solvents (acetone, ethanol, acetonitrile, dimethyl sulfoxide, and water) via an implicit solvent model.

Multicomponent Phase Separation in Ternary Mixture Ionic Liquid Electrolytes.

We investigate the phase behavior of ternary mixtures of ionic liquid, organic solvent, and lithium salt by molecular dynamics simulations. We find that at room temperature, the electrolyte separates into distinct phases with specific compositions; an ion-rich domain that contains a fraction of solvent molecules and a second domain of pure solvent. The phase separation is shown to be entropy-driven and is independent of lithium salt concentration.